View Compilation Error

0_0_18798388_13746.cpp:5:1: error: 'String' does not name a type
 String change(string s)
 ^
0_0_18798388_13746.cpp: In function 'int main(int, char**)':
0_0_18798388_13746.cpp:30:38: error: 'change' was not declared in this scope
   if(loc !=string::npos) s1=change(s1);
                                      ^
0_0_18798388_13746.cpp:32:38: error: 'chsnge' was not declared in this scope
   if(loc !=string::npos) s2=chsnge(s2);
                                      ^
0_0_18798388_13746.cpp:34:17: error: 'end1' was not declared in this scope
    cout<<"YES"<<end1;
                 ^
0_0_18798388_13746.cpp:36:16: error: 'end1' was not declared in this scope
    cout<<"NO"<<end1;
                ^